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Geophysical Research Abstracts
Vol. 19, EGU2017-10626, 2017
EGU General Assembly 2017
© Author(s) 2017. CC Attribution 3.0 License.
Utilisation of Sand from Kaolin Washing for the Manufacture of
Alkali-activated Artificial Sandstone
Martin Vavro (1), Leona Vavro (1), Pavel Mec (2), Kamil Soucek (1), Frantisek Pticen (3), and Pavel Reiterman
(4)
(1) Institute of Geonics of CAS, Ostrava, Czech Republic ([email protected]), (2) VSB - Technical University of
Ostrava, Ostrava, Czech Republic ([email protected]), (3) KERAMEX Group, Karlovy Vary, Czech Republic, (4) Czech
Technical University in Prague, Experimental Centre, Czech Republic ([email protected])
Sandstones represent a traditional natural stones which are widely used in Czech architecture and sculpture over a
long time. Thanks to their relatively easy workability, sandstones provide a wide range of stone products and also
represent a popular material for architectural and sculptural purposes. In the field of restoration of artworks, they
are therefore often used for manufacturing stone statue copies originally made from the same or similar type of
stone. Despite a relatively common and varied occurrence of natural sandstones, the method of the artificial stone
facsimiles creation in the form of various cast elements is also often applied in restoration practice. The history of
application of artificial stones in civil engineering and architecture goes back to the ancient times, i.e. to Roman
antiquity and possibly up to the time of ancient Egypt. The lack of appropriate natural rock, suitable in the view
of colour, grain size or texture is the main reason of manufacturing copies based on synthetic mixtures. The other
reason is high financial costs to create a sculpture copy from natural materials. Mixtures made from white and/or
grey cements, sands, carefully selected crushed stone or well graded natural gravels, and mineral coloring pigments
or mixtures with acrylate, polyester, and epoxy resins binder are the most frequently used artificial materials for
cast stone manufacturing.
This paper aims to bring information about composition and properties of artificial sandstones made from alkaliactivated binder mixtures based on metakaolin and granulated blast furnace slag. The filler of this artificial stone
is represented by fine-grained sand generated during kaolin wet processing. Used sand is mainly formed by
quartz, feldspars, micas (muscovite > biotite), residual kaolin, and to a lesser extent also by Fe oxyhydroxides
(“limonite”), titanium dioxide mineral (probably anatase), and carbonate mineral unidentified in detail. Annual
Czech production of this sand from kaolin-washing process is of several hundred thousand tonnes and it thus represent so far a relatively rarely used natural building material which is currently usually deposited in worked-out
areas of kaolin quarries. One of the main reasons of very difficult usability of this sands in building material industry is their behavior when exposed to the weather. In only a very short time of exposure in outdoor condition they
may change in colour from greyish white to yellow-brown or golden yellow. This colour change is accompanied
by significant decrease of pH values of sand leachate up to pH ranging between 3.5 and 5.5, in extreme cases even
up to 2.0.
Despite these extreme chemical properties of sands under study, the artificial sandstone, very similar in the physical
and mechanical properties to natural ones, was successfully prepared in the laboratory. Due to the mineralogical
composition of applied sands (i.e. the presence not only of quartz, but also of feldspar and muscovite), the artificial
sandstone is characterized by relatively true natural appearance.